Boiler furnace wall construction



Aug. l1, 1953 w J. KuNz BOILER FURNACE WALL CONSTRUCTION 2 Sheets-Sheet1 Filed Jan. 22, 1947 AA v Kunz

Aug 11, 1953 w. J. KuNz l2,648,315

BOILER FURNACE WALL CONSTRUCTION Filed Jan. 22, 194'? 2 Sheets-Sheet 2Fig. Q 9 INVENTOR Willi J. K nz WM Patented Aug. 1.1K, 1953 UNITEDSTATES 4PATE-NT OFFICE William J. Kunz, vv"Port Washington, N.Y.,1assi'g`nor to Combustion Engineering, lne., a corporation ofDelaware Application urinary 22, roimse'rilNo."#3344 4 Claims. l vThisVinvention relates `to furnace Walls `:and'fin particular to furnaceWalls Whose inner faces are lined with fluid-cooled tubes, as inthefurnaces .for steam generators.

A satisfactory construction of furnace walls-- Vfor a steam generatorcomprises 'an inner lining of fluid-cooled tubes which `are'exposed ontheir inner sides to the heat from the burning fuel and are covered ontheir outers'ides Withalayer of refractory material backed by Vva layer'of in-" sulation and the Whole 1'Ii/al1 structure covered by a Asteellcasing built 'sufficiently strong jto ire? sist furnace pressures.`Because of the cost "of this steel enclosed construction there have`'been increased requests for less expensive Walls "of 1" plasticconstruction. i

In general, the plastic walls as "heretoforefconstructed, are made inone homogeneous mass,

necessitating the expansion and contraction rof the entire Wall as aunit. Because of the variaf Figure 1 is a fragmentary elevation fofthejout- A yside of a furnace Wall embodying *my iimgiroved structure;

Figure 2 is an enlarged fragmentary'elevation of a typical panel shownin Figure 1;

Figure 3 is an enlarged section 'in elevation taken on line 3-3 ofFigure 1*; and

Figure 4 is a section taken on line '1l-4 "of Figure 2.

The furnace Wallhere illustrated'lcomprisesla row or bank of verticalduid-cooled tubes lI linn ing the outside of the furnace. Thesetubsareexposed on their inner sides to Jthe heat*f ro'rn the burning fuel, thetemperature'of `'combustion being generally Well over 2000 deg. F. -Ins'tea'rn generators such furnace tubes are connectedjfor iiow of coolingfluid therethrough, into "Water circulation With the boiler`in aw'ellknown inanner, The tubes lI may be arranged in'a'iowlli'n side by siderelation as sho'y'vii'inthe"left`half of Figures 2 and 4 or they may 'bein spaced 'apart 'relation yas shown in the right half of said figures.-In vthe latter arrangement they are pref- 'erably provided with Welded-on `fins 2 which Ypr-oject into Vthe intertube space to substantiallyclose the 'gap ibetween 'tu-bes. These Ifins 4absorb heat Awhich flowsto 'the tubes land into the ywater therein. A

On the outer side of -the rowof tubes I there is provided an inner,-x'ne'tal -reinforced ls'lfab 3 of 'plastic refractory lin*after-iai,the reinforcingme'tal 4 being preferably 'an expanded met'al Ao'r fheavywire mesh. This reinforced slab 3 extends continuously "over the "entireoutside 'surfacefof 4the ytube Wall andis of substantially uniformthickness, forming va 'ijnono'lithic `=1ay`er lor backing to the tubes.uIncase thetubes I are larranged in side vby side relationas-shown onthe 'left half `of 'Figure "4, 1the plastic of Slab3 `inay extend 'intolthe spaces between tubes. '--In case the tubes I are arranged 'infspaced "apart relation as `shown yin 'the right half of Figure '4, the'intertube space 5 between the fins=2 andfthe plane tangent to-the vbacksof the tubes vis :preferably Vfilled in byv high 'heat resistingrefractorylblocks shaped tot into the space or Aby "a plastic of `saidrefractory material.

yThe plastic l"slab j3 fis of substantial thickness and due to itsreinforcement resists bending vas Well as cracking. The slab`3 willcooperate-with the remainingjwall structure, to 'be hereafter described,`in resisting and distributing the-pres- "sures vboth Linternal andexternal of the furnace yThe reinforcing v4, orzex'p'anded metal, islspaced from the backs of the tubes vby vStuds 'f6 Whic'hare `Welded toYthe tubes and Iei'itend rearwardly therefrom. '-The reinforcingis heldinlplace and is supported bystudsfli as by nuts 'andwashers for othersuitable fastening 'devices fl. IIn this manner the entire inner slab 13is supported'by and securedl to the tube-bank I.

The inner-"slab "3 approaches the -ave'rageiternperature of the'rearward portiony of the fluidlcooled steel tubes and ns. Thelexpansion of vthe tubes I and the refractory 4material -3-1and thereinforcing steel t-arefsubstantially the saine for 'the -same v`rangein temperature. Consequentlythe bank of "tubes'I andslab '3 expandtogether in directions parallel'v to the tube bank and anyinjuriousexpansion strains between the two to causecracks -are'thereb'yavoided.

Spaced vfrom and parallellt'o' theiinner -Wall slab 3 is an outer,'metal 'reinforced slab'of plastic material and similarinconstrutiontoithe'inner slab 3. Preferably. expanded rnetalor heavy Wire'mesh reinforcing '9 'is used. "This outer rreinforced slab 8 issupported from an outer structure of steelwork I independently of thetube bank and the inner slab 3. Intermediate the inner and outer slabs 3and 8 is a layer of heat insulating material II which preferablycomprises 'a multiplicity of rectangular blocks placed side by side toll the entire inter slab space.

The outer steel structure I9 of the illustrated example, compriseshorizontally spaced, vertical bars I2 which are suspended in a wellknown manner from steel beams (not shown). At spaced vertical intervalsalong the length of bars I2 are horizontal buckstays I3 extending acrossthe width of the furnace wall and fastened, at the corners of thefurnace, to the corresponding buckstays of the adjacent walls to form awall stiffening, girth member around the furnace which maintains thealignment of all wall members and is capable of resisting any outwardpressure exerted by possible internal explosion.

The buckstays I3 or channels are fastened to the bars I2 as by angleclips I4. To each buckstay I3 is fastened, such as by welding 30, agirth plate I5 extending flush within the outer surface of the outerslab 8. The sheets of expanded metal reinforcing 9 of the outer slab 8extend partly across the back of girth plate I5 from above and below andare clamped thereto for support by a multiplicity of small plates I6which are placed on the inner sides of the reinforcing 9 and held to thegirth plate I5 by bolts I1.

Intermediate the buckstays I3 and between bars I2, are a multiplicity ofvertically spaced, horizontal stiffeners I8 fastened at their ends tovertical bars I2 as by clips I9 and bolts 20. Fastened to the inside ofeach stiffener I8 are plates 2| which lie within the outer slab 8 and towhich the reinforcing 9 of the outer slab is fastened as by wirespassing through holes 22. In this manner the entire outer slab 8 issupported and stiifened by the outer steel structure I0.

The girth plates I5 of buckstays I3 have `angle clips 23 fastened totheir inner sides at horizontally spaced intervals (Figures 2 and 3).One leg of the clips 23 extends inwardly to act as a support for blocksof-heat insulation II between the inner and outer slabs 3 and 8.

To maintain 4a fixed spaced relation between the inner and outer slabs 3and 8, each girth plate I5 is provided with a multiplicity ofhorizontally spaced, spacing means. In the illustrated form, eachspacing means comprises a spacing bolt 24 rigidly fastened to girthplate I5 as by nuts 25 and extending inwardly with its head adjacent theouter side of the furnace tubes I. A vertically slotted channel member26 is fastened, as by Welding, to a furnace tube I, located with itsslot straddling the spacing bolt 24 and spaced from the tube to allowthe head of the bolt to freely move between the slot and tube. The widthof the slot is greater than the diameter of the spacing bolt 24 to allowfor some relative horizontal as Well as vertical movement, and a washer2l prevents the bolt head from passing through the slot. The spacingbolts 24 are adjusted by means of nuts 25 to snugly contain theinsulation II between the inner and outer slabs 3 and B. The spacingmeans described above is similar to that shown in the U. S. patent to W.J. Kunz et al. No. 2,223,215, issued November 26, 1940, and also servesto hold the furnace tubes in spaced alignment with the furnace steelworkI0.

In operation, wheen fuel is being burned within the furnace, the innerslab 3 approaches the average temperature of the rearward portion of thetubes and fins and the entire structure including the tube bank and slabexpand together without injurious expansion strains which may causecracks. The outer slab 8 approaches the temperature of the boiler roomand its movement due to expansion is entirely independent of that of theinner slab 3. The outer surface of the inner slab 3 and the innersurface of the outer slab 8 constitute substantially parallel planesbetween which is held the insulation I I. The outer surface of the innerslab 3 that adjoins the insulation II provides a plane along whichrelative movements occur due to different expansions of the inner slaband the outer slab with respect to the installation.

Obviously if desired, the inner reinforced plastic slab 3 may be used incombination with an outer steel casing structure in place of the outerreinforced slab 8 as described.

While the preferred embodiment of my invention has been shown anddescribed, it will be understood that changes in construction,combination and arrangement of parts may be made without departing fromthe spirit and scope of the invention as claimed.

What I claim is:

1. In la furnace wall, the combination of fluidcooled tubes disposedalong the walls inner face in heat receiving relation to the furnacecombustion chamber; an inner monolithic slab of plastic refractorymaterial positioned against the backs of said tubes and having expansioncharacteristics which substantally match those of said tubes over therange of temperatures encountered during furnace operation; mesh-likereinforcing metal incorporated into said slab; stud bolts welded to thebacks of said tubes and extending into the slab and cooperating withsaid reinforcing metal to secure said inner slab to the tube backs andto support said slab from said tubes for expansion and contractiontogether therewith; an outer slab of plastic refractory materialpositioned substantially parallel to said inner slab in spaced relationthereto and having reinforcing metal incorporated therein; said outerslab also comprising a layer of heat insulating material lling theaforesaid space between the inner and outer plastic slabs and serving toseparate same in a way which permits relative movement between the slabsalong the inner slab surface that adjoins the insulating layer and whichlatter causes the outer plastic slab temperature to be substantiallyindependent of the inner slab temperature; an external structure forholding said outer plastic slab in its aforesaid position and forstiifening said entire wall against movement outwardly from the furnacecenter, said structure comprising spaced buckstay, stiffening andsupporting members disposed adjacent the outer slabs exterior surface;and means cooperating with the outer slabs reinforcing metal and withthe heat insulating material, for supporting said insulating materialfrom the aforesaid external structure and for fastening said outer slabto the said external structure so as to provide for outer plastic slabstiffening and support which is independent of the earlier describedsupport derived by said inner plastic slab from the furnace tubeswhereby each of the aforesaid inner and outer slabs is permitted toexpand and contract independently of the other without transmission ofresultant movements therebetween or inducement in either slab ofinjurious mechanical stresses due to temperature differentialsencountered during furnace operation.

2. A furnace wall comprising a layer of parallel side by side tubesmaking up the inner surface thereof, a reinforced plastic refractoryslab supported from and positioned against the back of these tubes andhaving expansion characteristics substantially matching those of thetubes, a second reinforced plastic slab spaced outwardly of the firstmentioned slab, heat insulation disposed in the space between the twoslabs, outer support structure supported independently of the tubes andsecured to the reinforcing of the outer slab thereby supporting the sameindependently of the tubes, and means effectively secured to the outersupport structure and associated with said heat insulation forsupporting the same from said structure.

3. A furnace wall comprising a plurality of parallel tubes arranged inside by side relation and making up the inner face of said wall; aninner slab of plastic refractory material having expansioncharacteristics the same as those of the tubes and having reinforcingWire mesh embedded therein; studs disposed between certain of said tubesand said reinforcing means and secured to both thereby supporting saidinner plastic slab from said tubes whereby the two move in unison; anouter plastic slab lying parallel to and spaced outwardly from saidinner slab and having reinforcing wire mesh, embedded therein; steelstiffening and support members positioned adjacent the outer surface ofthe outer slab and supported independently of said tubes, said membersincluding bars disposed parallel to said tubes and buckstays disposedtransversely of said tubes, said bars and buckstays being effectivelysecured to the reinforcing in said outer slab thereby supporting saidouter slab; means effective to maintain the spacing between the tubesand the outer slab substantially constant while permitting limitedrelative movement; a rigid insulating material disposed within and llingthe space between said slabs; and means effectively secured to saidbuckstays for supporting said insulating material whereby it moves inunison with the outer slab and steel support members.

4. A furnace wall as defined by claim 3 wherein the buckstays areprovided with girth plates disposed in the plane of the other plasticslab and to which the reinforcement in said slab is secured, and whereinthe means for supporting the insulating material disposed in the spacebetween the slabs comprises angular members secured to said girth plateand projecting into said insulation.

WILLIAM J. KUNZ.

References Cited in the le of this patent UNITED STATES PATENTS FOREIGNPATENTS Country Date Great Britain June 11, 1935 Number Number

